The Breast Cancer Program at the University of Southern California (USC)/Norris Comprehensive Cancer Center (NCC) is a focused interdisciplinary research program devoted to breast cancer. The scientific aims of the program are 1) to Test hypotheses of breast cancer etiology and pathogenesis with a particular emphasis on diverse racial/ethnic groups within Los Angeles County, 2) To identify differences in breast cancer mortality among racial ethnic groups of Los Angeles County and formulate strategies to lower mortality among all groups. 3) To characterize molecular genetic alterations in breast cancers with a focus on potential clinical utility, 4) To formulate and assess various strategies for breast cancer prevention, and 5) To develop and/or evaluate novel therapies for breast cancer; to enroll patients on local or national therapeutic protocols related to breast cancer, particularly emphasizing minority patient recruitment. The USC/Norris Breast Cancer Program takes advantage of the extraordinary, racial-ethic diversity among the 10 million residents of Los Angeles County, the population served by the NCCC. A major goal of the Program is to better understand the reasons for the underlying differences in breast cancer incidence, mortality and survival among the numerically most important of these racial-ethnic groups in the County (African-Americans, Latinas, Japanese, Chinese, Filipinas, Koreans and non-Latina whites). We have a multifaceted approach involving epidemiology and prevention scientists, behavioral scientists, tumor biologists and molecular geneticists, and radiation surgical and medical oncologists. Numerous patient and data resources are used to achieve this goal. These include the Los Angeles County SEER cancer registry program; a registry of breast cancer in twins; dietary and lifestyle data from recently characterized large racial- ethnically diverse cohorts; a large and diverse clinical population seen at NCCC affiliated hospitals; and several large tumor and other biological sample banks for studies of tumor biology and molecular genetics. The integrated multi-disciplinary Lee Breast Center has been built in the Hospital providing an environment favorable to patient care and clinical research. Recruitment of study subjects to clinical investigations has been strengthened during the last funding period. The overall annual research budget for the Program is in excess of $7 million. Four members of the Breast Cancer Program have been named to endowed Chairs in the NCCC. Funding has been provided for recruitment of new faculty, an annual program retreat, pilot research projects, and startup research funds for recruited faculty.